Pump module and positive displacement pump

ABSTRACT

A pump module ( 4, 5, 6; 4′, 4 ″) includes a housing ( 14 ) that limits at least one channel ( 17 ) connecting at least one inlet with at least one outlet, an elastic membrane ( 18; 21; 22 ) extending in the housing in a flow direction, and a plurality of actuators located in the housing opposite each other on both sides of the at least one flow channel and forming actuation stages (A 1 -A 6 ) arranged one after another in the flow direction, with a respective section of the elastic membrane being deflected and abutting a respective circumferential section of the at least one flow channel upon activation of an actuator of a respective actuation stage for forming a delivery chamber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pump module having a housing with atlest one inlet and at least one outlet, at least one channel located inthe housing and connecting the at least one inlet with the at least oneoutlet, pumping element extending in the housing in a flow direction, aplurality of individually activated actuators for sectionally deflectingthe pumping element, and at least one delivery chamber for enclosing adelivering medium and which becomes encapsulated between sections of thepumping element and corresponding circumferential sections of the atleast one flow channel upon sequential activation of the actuators andin course of a delivery movement is displaced between the at least oneinlet and at the at least one outlet. The present invention also relatesto a positive displacement pump for delivering a fluid in which at leastone above-mentioned module is used.

2. Description of the Prior Art

In positive displacement pumps, usually, medium that flows into the pumpinterior through an inlet, is encapsulated in the delivery chamber andis finally displaced into an outlet. In order to prevent backflow of themedium into the inlet during this displacement and to exclude backsuction of the already displaced medium, there is provided apressure-operated valve for controlling at least one of the inlet oroutlet or similar means. This, however, increases the number ofcomponents and, in addition, makes it more difficult to achieve a lowend pressure. This is because the valves are mainly operated based onthe pressure difference and, at a low pressure, no sufficiently highpressure forces can be provided in the valve region. In addition,dependent on the type and manner of the delivery movement, frictionlosses and vibrations occur. Usually, the positive displacement pumpsare equipped partially with pump modules, with which the number ofcomponents is reduced and the delivery movement is obtained in a mostsimple way.

Japanese Publication JP 03-081585 discloses a pumping module having ahousing that limits a cuboid flow channel. The flow channel connects aninlet and an outlet and has a pumping element located therein. Thepumping element is oriented in the flow direction and is formed of aplurality of piezoelectrical actuator sections arranged in a row oneafter another and forming a lamella located in the flow channel. Uponactivation of individual piezoelectrical actuator sections, the lamellais sectionally deflected, abutting respective sections of thesurrounding housing, enclosing to-be-delivered medium within arespectively formed, as a result of deflection, delivery chamber. Withsequential activation of the piezoelectrical actuators, the enclosed inthe respective delivery chamber, medium is displaced, in the course of aperistaltic delivery movement, from the inlet to the outlet.

Proceeding from the above-discussed state-of-the-art, the object of theinvention is to provide a pump module with which a precise deliverymovement is achieved together with simplification of the structure.

SUMMARY OF THE INVENTION

The object of the invention is achieved, according to the invention,with a pump module having a housing with at least one inlet and at leastone outlet, at least one channel located in the housing and connectingthe at least one inlet with the at least one outlet, and a pumpingelement extending in the housing in a flow direction. A plurality ofindividually activated actuators sectionally deflect the pumpingelement. The pump module further has at least one delivery chamber forenclosing a delivering medium and which becomes encapsulated betweensections of the pumping element and corresponding circumferentialsections of the at least one flow channel upon sequential activation ofthe actuators and in course of a delivery movement is displaced betweenthe at least one inlet and the at least outlet.

The pumping element is formed as a washer-shaped, plate-shaped or thelike component that can be sectionally deflected, with separate segmentsbeing displaced orthogonally to the longitudinal extension of thepumping element by the actuators. With this, dependent on the number ofthe deflected sections of the pumping element, one or more deliverychambers become enclosed with one or more circumferential sections ofthe flow channel, with a to-be-delivered medium being enclosed in therespective delivery chamber. According to the invention, the deliverymedium is, in particular, a fluid, such as gas or a gas mixture, orliquid, or a liquid mixture. By a sequential activation of theactuators, the at least one delivery chamber is displaced between the atleast one inlet and the at least one outlet of the pump module, so thatthe enclosed therein to-be-delivered medium is delivered from inlet tothe outlet. This delivery movement is similar, with a correspondingactivation of the actuators, in particular, to peristaltic movement ofthe pumping element.

The present invention includes teachings according to which theactuators are located in the pump module housing opposite each other onboth sides of the at least one flow channel and form actuation stagesarranged one after another in the flow direction. Further, the pumpingelement is formed as an elastic membrane that, upon activation of anactuator of a separate actuation stage, has a respective section thereofabutting a respective circumferential section of the flow channel. Withother words, the actuators, with which the pumping element that islocated in the flow channel, can be sectionally deflected, are placed inthe surrounding housing and are pair-wise combined to form actuationstages. The respective associated actuators are located on both sides ofthe flow channel, i.e., one actuator of an actuation stage is positionedabove the flow channel, and the other actuator is positioned below theflow channel. Altogether, the actuation stages are arranged one afteranother in the flow direction so that upon moving along, the individualactuation stages are passed over. The pumping element, which is formedas an elastic membrane, thus, can be sectionally deflected when anactuator of an individual actuation stage is activated, with a sectionof the membrane located between the actuators of this actuation stagebeing deflected, abutting the located there, circumferential section ofthe flow channel.

The inventive pump is characterized by a simple construction, withsimultaneously a reliable functioning. By placing the actuators in thestationary housing, they can be activated in simple manner withconductors running in the housing, with these conductors being chamberedfrom the flow channel and the medium delivered therethrough. Due to themanner of the flow movement, the valves on the inlet side and the outletside can be dispensed with because the to-be-delivered medium isencapsulated between the elastic membrane and the circumference of theflow channel due to the sectional deflection of the elastic membrane.The membrane is a sole movable component so that with an appropriateoptimization, a long service life of the inventive pump module can beachieved. Besides, the membrane, being an elastic component, can beprecisely deflected and abut the circumference of the flow channel,whereby the respective delivery chamber can be precisely defined andsealed. Further, the pumping frequency of the pump module and thepumping sequence, i.e., the definition of the size of the at least onedelivery chamber, can be freely adjusted with the actuators, which makesthe inventive pump module universally suitable for differentapplications, with the activation of the actuators being varieddependent on the desired delivery. All in all, the inventive pump moduleis characterized by a simple construction, together with lowmanufacturing costs and low noise generation.

In distinction therefrom, in JP 03 081 585 A, the actuation of thepumping element that is located in the flow channel, is more difficultbecause for the sectional deflection of the piezo-sections provided inthe lamella-shaped components, they should be correspondingly energized.To this end, corresponding contacts need be provided or conductorsshould be lead up to the deflectable pumping element, which complicatesthe construction of the pumping module and, as a result, increasesmanufacturing costs. Further, the lamella which is provided withpiezo-elements is less flexible than the membrane, with the definitionof the delivery chambers being strictly defined in accordance with thesize and arrangement of the piezo-sections. Therefore, a pumpingsequence cannot be individually adapted to separate applications.

Also, the nestling of the lamella against the circumference of the flowchannel is less precise than with an elastic membrane.

According to an advantageously embodiment of the present invention, theactuators are formed as solenoids. Those are surrounded by a materialthat has a high permeability, e.g., iron, and produce, upon beingenergized, a magnetic field that deflects respective sections of theelastic membrane. In order to achieve the sectional deflection of themembrane in the magnetic field, the membrane is formed of amagnetorheological elastomeric material or an elastomeric material withferromagnetic material integrated in sections associated with theactuation stages. A magnetorheological material is a composite materialof a weak elastomer matrix with magnetically polarized particlesembedded therein which can be subjected to action of the magnetic field.In case when the membrane is formed of an elastomeric material withferromagnetic particles embedded therein, according to the invention,metal sheet segments are cast over by the elastomeric material, forminga connection system.

According to an alternative embodiment of the invention, the actuatorsare formed by electrodes. Upon being energized, these electrodes producean electrical field which again can sectionally deflect the elasticmembrane. To this end, the elastic membrane is formed in particular ofan electrorheological material of an elastomer with embedded thereinparticles which are pulled in the electrical field in direction ofrespective energized electrodes, causing a corresponding sectionaldeflection of the elastic membrane.

According to a further embodiment of the invention, the pump modulehousing is formed of two housing parts, wherein the housing parts andthe membrane, which lies therebetween, are formed as discs having acircular cross-section. Further, the at least one inlet is providedradially outwardly and is connected by the flow channel with the atleast one outlet which is arranged centrally in the radial direction. Inthis case the pump module has a circular shape, with the deliveredmedium being delivered from radially outwardly to radially inwardly tothe outlet. According to the invention, the inlet can likewise be placedcentrally, and the outlet can lie radially outwardly. With the circularconstruction of the pump module, a plurality of pump modules can bearranged without problems one after another, with the separate circularpump modules being axially stacked one above the other and dependent onthe desired switching, form a parallel arrangement of separate inlets,or have at least one outlet of one module connected with at least oneinlet of the following module in form of a series connection. With acircular construction of the pump module of circular discs, theactuators are correspondingly ring-shaped, i.e., are formed asring-shaped solenoids or ring-shaped electrodes. Alternatively, togetherwith a circular construction, in principle, a rectangular constructionof the pump module can also be contemplated.

According to a further development of the invention, the actuationstages can be arranged, in the flow direction, equidistantly or atdifferent distances relative to each other. Dependent on theconstruction of the pump module and the type of the deliverable medium,the at least one delivery chamber can have, during its movement betweenthe at least one inlet and the at least one outlet, a constant orvariable volume. In this way, a medium in form of gas or a gas mixturecan be compressed during its movement from at least one inlet to the atleast one outlet. At a circular construction of the pump module, thedistances between the actuation stages are selected so that they areequidistant, so that with at least one delivery chamber, upon movementfrom a radially outwardly located inlet to a centrally located outlet,its volume continuously diminishes because of ever smaller annularsurfaces between the actuation stages, and compression of the gas takesplace. Similarly, with a rectangular construction, with differentdistances between the actuation stages, a continuously diminishing ofthe at least one delivery chamber occurs.

If the deliverable medium is liquid, because of the incompressibility ofthe liquid, usually, the reduction of the volume of the at least onedelivery chamber is not desirable. This volume can be kept constantduring movement between the at least one inlet and the at least oneoutlet, with a circular construction of the pump module, by placing theseparate actuation stages at different distances from each other in theflow direction for forming identical ring surfaces, or with arectangular construction of the pump module, by selecting the samedistances between the actuation stages. Finally, a delivery of a liquid,at a circular construction of the pump module and an equidistantdistances between the actuation stages, is also possible when the atleast one inlet is centrally located in the flow direction, and the atleast one outlet is provide radially outwardly, so that the volume ofthe at least one delivery chamber increases during movement between theinlet and the outlet.

Different or the same volumes of the delivery chamber can also beachieved by a corresponding adjustment of the pump frequency. Becauseencapsulation and movement of a respective delivery chamber iscontrolled by activation of respective actuation stages, the size andthe change of the delivery chamber can be adjusted substantially freelyby varying activation of the actuation stages. Thus, the compression ofthe medium, which otherwise takes place, based on the spacing betweenthe actuation stages and the construction of the pump module, duringmovement of the delivery chamber, is thereby increased or reduced, sothat at the outlet side or respective desired pressure level of themedium is achieved.

A positive displacement pump according to the invention includes atleast one pump module according to one of the embodiment discussedabove. The positive displacement pump is formed in particular as avacuum pump that serves for delivering a fluid. Advantageously, severalpump modules, which are arranged seriesly and/or parallel to each other,are arranged in the pump housing, so that individual pump model, whichare arranged parallel to each other or follow one another, deliver fluidto a common outlet.

According to a further advantageous embodiment of the invention, theactuators of at least one pump module are controlled by powerelectronics. With such power electronics, different pump frequenciesand, also, pump sequences can be obtained without problem bycorresponding activation of the actuators. However, activations ofseveral pump modules, which are correspondingly adapted to each other,can also be carried out. Apart from the power electronics associatedwith one of the pump modules, a corresponding electronic of another pumpsuch as, e.g., turbomolecular pump, or of another system can be used.

A positive displacement pump according to one of the above-describedembodiments can be used in a recipient as a vacuum pump, in particular,for obtaining low and high vacuum. Further, a positive displacement pumpformed, according to the invention, as a vacuum pump can be used as afore-vacuum pump of a high and/or ultra-high vacuum pump, in particular,of a turbomolecular pump.

The present invention is not limited to the discussed combination ofrelated claims or dependent claims. In addition, there exist a number ofpossibilities to combine with each other separate features which followfrom the claims, the description of different embodiment of theinvention, and/or the drawings. The reference in the claims to thedrawings by the use of reference numerals does not limit the scope ofthe claim in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantageous embodiments of the invention will be described indetail below with reference to the accompanying drawings.

The drawings show:

FIG. 1 a schematic view of a first preferred embodiment of a positivedisplacement pump according to the invention;

FIG. 2 a schematic view of a first embodiment of a pump module of thepositive displacement pump shown in FIG. 1;

FIG. 3 a view illustrating separate switching sequences of the pumpmodule shown in FIG. 2;

FIG. 4 a schematic view of another embodiment of a pump module of thepositive displacement pump shown in FIG. 1;

FIG. 5 a schematic view of yet another embodiment of a pump module ofthe positive displacement pump shown in FIG. 1;

FIG. 6 a schematic view of a second embodiment of a positivedisplacement pump according to the invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a schematic elevational view of a positive displacementpump according to the first embodiment of the invention, wherein thepositive displacement pump is a vacuum pump and, preferably, afore-vacuum pump of a turbomolecular pump. The positive displacementpump includes a pump housing 1 in which between a lateral inlet side 2and an end outlet side 3, there are provided a plurality of identicallyformed pump modules 4, 5 and 6. The pump modules 4-6 are formed ascircular, rotationally symmetrical modules which are connected,respectively, with the inlet side 2 by their ring-shaped inlets 7, 8 and9, and are commonly connected with the outlet side 3 by respectivecentrally located outlets 10, 11, 12. The pump modules 4-6 are, thus,arranged in the pump housing 1 parallel to each other and deliver afluid, in particular, in form of an air mixture from the inlet side 2 tothe outlet side 3. Further power electronics 13 which can control theseparate pump modules 4, 5, 6, is also located in the housing 1.

FIG. 2 shows a schematic elevational view of a pump module 4 theconstruction of which, however, corresponds to that of the pump modules5 and 6. The pump module 4 has a housing 14 formed of two housing parts15 and 16 which a formed as discs having a circular cross-section andlimit a flow channel 17 extending therebetween, with the housing parts15 and 16 being chambered from each other. The flow channel 17 connectsthe ring-shaped inlet 7, which is only suggested, with the centraloutlet 10. In FIG. 2, for the sake of clarity, in the radial direction,only half of the pump module 4 is shown. Over the flow channel 17, fluidcan flow radially through the housing 14 from the inlet 7 and thenaxially through the outlet 10 to the common outlet side 3 shown in FIG.1.

A membrane 18 is located in the flow channel 17 and which is locatedbetween the two housing parts 15 and 16 and is shown in FIG. 2 in itsrest position. To this end, the membrane 18 is clamped in a suitablemanner between the housing parts 15 and 16, e.g., in the region of thering-shaped inlet 7. The membrane 18 is likewise formed as a disc with acircular cross-section and is formed of an elastomeric material in whicha plurality of sheet rings B1-B6, which are concentrically arrangedabout the outlet 10, are integrated.

As further shown in FIG. 2, in the radial direction over the height ofthe sheet rings B1-B6, there are further provided a plurality ofactuator stages A1-A6 which are arranged one after another in the flowdirection from the inlet 7 to the outlet 10. Each actuator stage A1-A6is formed of two actuators arranged on opposite sides of the flowchannel 17 and on opposite sides of respective sheet rings B1-B6. Theactuators of the actuator stages A1-A6 are formed of located oppositeeach other, solenoids M1.1-M6.2 which are surrounded by iron and arecombined in pairs, forming the actuator stages A1-A6. The powerelectronics 13 energizes the actuator stages A1-A6, energizing thecombined in pairs, solenoids M1.1 or M1.2 or M2.1 or M2.2 or M3.1 orM3.2 or M4.1 or M4.2 or M5.1 or M5.2 or M6.1 or M6.2, so that respectivesolenoids produce a magnetic field attracting respective, locatedtherebetween, sheet rings B1 or B2 or B3 or B4 or B5 or B6 thereto,sectionally deflecting the membrane 18. With this, the membrane 18 abutsthe housing parts 15 or 16 with a respective section and, thus, acircumferential section of the flow channel 17, whereby with acorresponding control of separate solenoids M1.1-M6.2, delivery chambersare defined between the membrane 18 and the housing parts 15 and 16.

FIG. 3 shows a complete, exemplary switching sequence for the pumpmodule 4 shown in FIG. 2. As can be seen, a delivery movement from theinlet 7 to the outlet 10 can be shown in five separate sequences,wherein the sequence 5 again corresponds to the sequence 1. A respectiveone of the solenoids M1.1 through M6.2 is actuated by separate actuatorstages A1 through A6, so that the intermediately located membrane 18have respective sections thereof deflected in this direction of thehousing part 15 or 16 and finally abuts the same. With altogether sixactuator stages A1 through 16, on one hand, delivery chambers 19, 19′can be defined between the membrane 18 and the housing part 15, and onthe other hand, delivery chambers 20 and 20′ can be defined between themembrane 18 and the housing part 16 which are movable from the inlet 7to the outlet 10 in the course of the pumping sequence.

This delivery movement, which is called peristaltic movement, will bedescribed, by way of example, with reference to the delivery chamber 19by respective separate sequences I through V on basis of FIGS. 2 and 3.Firstly, in the first sequence I, the delivery chamber 19 isencapsulated by energizing the solenoids M1.1, M2.2, M3.2 and M4.1,enclosing a corresponding amount of fluid between the membrane 18 andthe housing part 15. The delivery chamber 19 is then displaced, duringthe second sequence II, further in direction of the outlet 10, with thesolenoid M2.1 being energized instead of the solenoid M2.2 in theactuator stage A2, with the solenoid M4.2 being energized instead of thesolenoid M4.1 in the actuator stage A4, and with the solenoid M5.1 beingenergized in the actuator stage A5. For transition to a further sequenceIII, in comparison with the sequence II, in the actuator stage A3,instead of the solenoid M3.2, the solenoid M3.1 is energized, and in theactuator stage A5, instead of solenoid M5.1, the solenoid M5.2 isactuated. In addition, in the actuator stage A6, the solenoid M6.1 isenergized. Finally, in the sequence IV, the fluid located in thedelivery chamber 19 is fed to the outlet 10, and in which in comparisonwith the sequence III, in the actuator stage A4, instead of the solenoidM4.2, the solenoid M4.1 is actuated, and in the actuator stage A6,instead of the solenoid M6.1, the solenoid M6.2 is actuated. In thesequence V, a new cycle starts, with encapsulation of the deliverychamber 19′.

FIG. 2 shows that the actuator stages A1 through A6 are equidistantlylocated with respect to each other. In combination with the circularform of the housing parts 15, 16 and the membrane 18, the deliverychambers 19, 19′, 20, 20′ are continuously reduced in their volumeduring the radial delivery movement because the ring volumes toward theoutlet 10 defined between the actuator stages A1 through A6, becomecontinuously smaller. As a result, the fluid, which is located inrespective delivery chambers 19, or 19′ or 20, or 20′, becomescompressed as it is fed from the inlet 7 to the outlet 10. The powerelectronics 13 should insure a rapid exchange within each of theactuator stages A1 through A6 and between the actuator stages A1 throughA6 to reduce to a most possible extent pressure fluctuations in thedelivery chambers 19, 19′ 20, and 20 during movement toward the outlet10.

FIG. 4 shows an alternative embodiment of a pump module 4′ that can beused in the possible displacement pump of FIG. 1 instead of the pumpmodules 4-6. In distinction from the pump module 4 shown in FIG. 2, themembrane 18 is formed of a magnetorhelogical elastomeric material formedof an elastomer with integrated nanoscaled particles. In a magneticfield, a force acting on these particles provides for the desiredsectional deflection of the membrane 21 analogous to the deliverymovement described with reference to FIG. 3. In all other respects, thepump module 4′ shown in FIG. 4 corresponds to the pump module of FIG. 2.

FIG. 5 shows a further alternative embodiment of a pump module 4″ thatlikewise can be used in the positive displacement pump of FIG. 1 insteadof the pump modules 4-6. In distinction from the embodiment of FIG. 2,here, the actuator stages A1 through A6 are formed of pairs of locatedopposite each other electrodes E1.1 through E6.2. The electrodes E1.1through E6.2 can again be separately actuated by the power electronics13 to provide for the peristaltic delivery movement. In order to providea sectional deflection of a membrane 22 by an electrical field generatedby separate electrodes E1.1 through E6.2, the membrane is formed of anelectroheological elastomeric material formed of an elastomer withintegrated therein, nanoscaled particles. Under the action of theelectrical field, a force acting on these particles can cause again asectional deflection of the membrane 22. In all other respects, theconfiguration of the pump module 4″ of FIG. 5 is a variant of the pumpmodule 4 of FIG. 2.

Finally, FIG. 6 shows a schematic elevational view of a positivedisplacement pump according to the second embodiment of the invention.In distinction from the embodiment of FIG. 1, the pump modules 4-6 arenot arranged parallel to each other but are located seriesly, one afteranother in the flow direction. To this end, the inlet 7 of the pumpmodule 4 is connected with the inlet side 2 of the positive displacementpump, and the outlet 10 of the pump module 4 is connected with the inlet8 of the pump module 5. The outlet 11 of the pump module 5 again isconnected with the inlet 9 of the pump module 6 the outlet 12 of whichis connected with the outlet side 3 of the positive displacement pump.Here, the respective outlet 10, 11 or 12 is provided on an upper surfaceof the respective pump module 4, 5, 6, i.e., only the respective tophousing part 15 is provided in the center with an axially extendingthrough-bore. Generally, the configuration of the positive displacementpump of FIG. 6 is a variant of that according to FIG. 1.

With specific configuration of pump module 4-6 or 4′-6′; it becomespossible to simplify the construction while simultaneously insuring areliable operation of the medium delivery. Also, the inventive pumpmodule can be adapted, in any arbitrary manner to the configuration ofthe positive displacement pump. It is particularly useful in afore-vacuum pump or a forevacuum pump stage of a turbomolecular pump.

Though the present invention was shown and described with reference tothe preferred embodiments those are merely illustrative of the presentinvention and are not to be construed as a limitation thereof andvarious modifications of the present invention will be apparent to thoseskilled in the art. It is, therefore, not intended that the presentinvention be limited to the disclosed embodiments or details thereof,and the present invention includes all variations and/or alternativeembodiments within the spirit and scope of the present invention asdefined by the appended claims.

What is claimed is:
 1. A pump module (4, 5, 6; 4′, 4″), comprising ahousing (14) having at least one inlet (7, 8, 9) and at least one outlet(10, 11, 12); at least one channel (17) located in the housing (14) andconnecting the at least one inlet with the at least one outlet; anelastic membrane (18; 21; 22) extending in the housing in a flowdirection; a plurality of actuators located in the housing, theactuators being sequentially individually activated for sectionallydeflecting the elastic membrane for forming at least one deliverychamber (20, 21) between sections of the membrane and associatedcircumferential sections of the at least one flow channel for enclosinga to-be-delivered medium and movable, in course of a delivery movementbetween, the at least one inlet and the at least one outlet, whereinrespective actuators which are located opposite each other on both sidesof the at least one flow channel form actuation stages (A1-A6) arrangedone after another in the flow direction, with a respective section ofthe elastic membrane abutting a respective circumferential section ofthe at least one flow channel upon activation of an actuator of arespective actuation stage (A1-A6).
 2. A pump module (4, 5, 6; 4′)according to claim 1, wherein the actuators are formed by solenoids(M1.1-M6.2).
 3. A pump module (4, 5, 6; 4′) according to claim 2,wherein the membrane (18; 21) is formed of one of magnetorheologicalelastomeric material and elastomeric material with ferromagneticmaterial integrated in sections associated with the actuation stages(A1-A6).
 4. A pump module (4″) according to claim 1, wherein theactuators are formed by electrodes (E1.1-E6.2).
 5. A pump module (4″)according to claim 4, wherein the membrane (22) is formed of anelectrorheological elastomeric material (23).
 6. A pump module (4, 5, 6;4′; 4″) according to claim 1, wherein the housing (14) is formed of atleast two housing parts (15, 16), the membrane (18; 21; 22) which liestherebetween, is formed as a disc having a circular cross-section, andat least one inlet (7, 8, 9) faces radially outwardly, and at least oneoutlet (10, 11, 12) is arranged centrally in the radial direction.
 7. Apump module according to claim 1, wherein the actuation stages (A1-A6)are arranged, in the flow direction, equidistantly or at differentdistances relative to each other.
 8. A positive displacement pump fordelivering fluid, comprising at least one pump module (4, 5, 6; 4′, 4″),including a housing (14) having at least one inlet (7, 8, 9) and atleast one outlet (10, 11, 12); at least one channel (17) located in thehousing (14) and connecting the at least one inlet with the at least oneoutlet; an elastic membrane (18; 21; 22) extending in the housing in aflow direction; a plurality of actuators located in the housing, theactuators being sequentially individually activated for sectionallydeflecting the elastic membrane for forming at least one deliverychamber (20, 21) between sections of the membrane and associatedcircumferential sections of the at least one flow channel for enclosinga to-be-delivered medium and movable, in course of a delivery movementbetween the at least one inlet and the at least one outlet, whereinrespective actuators which are located opposite each other on both sidesof the at least one flow channel form actuation stages (A1-A6) arrangedone after another in the flow direction, with a respective section ofthe elastic membrane abutting a respective circumferential section ofthe at least one flow channel upon activation of an actuator of arespective actuation stage (A1-A6).
 9. A positive displacement pumpaccording to claim 8, comprising a housing (1), and a plurality of pumpmodules (4, 5, 6) arranged one of seriesly, parallel to each other, andseriesly and parallel to each other.
 10. A positive displacement pumpaccording to claim 8, comprising power electronics (13) for controllingactuators of the at least one pump module (4, 5, 6; 4′; 4″).
 11. Amethod of producing one of low and high vacuum in a recipient,comprising a vacuum pump formed as a positive displacement pump fordelivering fluid and comprising at least one pump module (4, 5, 6; 4′,4″), including a housing (14) having a pump module (4, 5, 6; 4′, 4″)comprising a housing (14) having at least one inlet (7, 8, 9) and atleast one outlet (10, 11, 12); at least one channel (17) located in thehousing (14) and connecting the at least one inlet with the at least oneoutlet; an elastic membrane (18; 21; 22) extending in the housing in aflow direction; a plurality of actuators located in the housing, theactuators being sequentially individually activated for sectionallydeflecting the elastic membrane for forming at least one deliverychamber (20, 21) between sections of the membrane and associatedcircumferential sections of the at least one flow channel for enclosinga to-be-delivered medium and movable, in course of a delivery movementbetween the at least one inlet and the at least one outlet, whereinrespective actuators located opposite each other on both sides of the atleast one flow channel form actuation stages (A1-A6) arranged one afteranother in the flow direction, with a respective section of the elasticmembrane abutting a respective circumferential section of the at leastone flow channel upon activation of an actuator of a respectiveactuation stage (A1-A6).
 12. A positive displacement according to claim8 and formed as one of vacuum pump and a fore-vacuum pump of one ofhigh, ultra high, high and ultra high vacuum pump and a turbomolecularpump.